The present invention relates to an improvement of a multilayer hybrid circuit which has a laminated printed circuit board including, at least, an inductor and/or a capacitor and/or a resistor in the printed circuit board itself.
Conventionally, electronic components are mounted on the surface of a printed circuit board, and the wiring among the components are effected through a printed wiring on the board. However, the high density mounting of electronic components requires improvements for mounting components.
The U.S. Pat. No. 4,322,698 provides one solution for high density mounting, and discloses a multilayer hybrid circuit which has a laminated printed circuit board which includes an inductor, a capacitor and/or a resistor. Since those components are produced in a board (not on the surface of the board), the size of the system can be miniaturized, and the high density mounting has become possible.
FIG. 8A and 8B show such prior multilayer hybrid circuits. In FIG. 8A, a laminated body 1A has a plurality of dielectric laminated layers 3 and a plurality of conductive films 4 so that those conductive films 4 those dielectric layers 3 compose a plurality of capacitors 5. A glass layer 6 is attached on at least one surface of the laminated body 1A, and a resistor network 9 which has a resistor layer 8 and a conductive layer 7 is attached on said glass layer 6. A printed wiring pattern 10 is deposited on at least one surface of the laminated body 1A, and a plurality of terminals 11 for external connection are deposited on the sides of the laminated body 1A. The conductive pattern 10 is used for mounting an electronic component 2 (for instance an integrated circuit, or a transistor) on the laminated body 1A. The laminated body 1A is produced through thick film printing process, and sintering process. An external electronic component 2 is soldered on the conductive pattern 10 by soldering a terminal wire 12 of the component 10 to the conductive pattern 10 by the solder 13.
In the prior structure of FIG. 8B, the laminated body 1B has not only capacitors and resistors, but also inductors 16 having an internal conductor 14 and a ferrite layer 15. In producing an inductor, a U-shaped conductive pattern 14a is printed and, next a ferrite pattern which is dielectric is deposited so that a window is kept at the one end of said U-shaped pattern 14a. Next, another U-shaped conductive pattern 14b is deposited on the ferrite pattern so that end of the pattern 14a at the window of the ferrite pattern is connected to the end of the second pattern 14b. Thus, a one turn coil is produced by a pair of U-shaped conductive patterns 14a and 14b. By repeating the above process, an inductor with a plurality of turns 14a and 14b is produced. Similarly, another inductor having U-shaped patterns 14c and 14d is produced.
However, a prior multilayer hybrid circuit has the following disadvantages.
(a) First, conventionally, a wiring between a surface component, and a capacitor 5, an inductor 16, or, a resistor 9, is effected by using a surface printed conductive pattern 10 and a side terminal 11 deposited on the surface of the laminated body. However, when a complicated external component 2 which has many external wiring pins is mounted on the board, the wiring pattern 10 must also be complicated. Thus, the area or the size of the board for the wiring pattern must be large, and sometimes that area required for wiring is larger than the area for mounting internal passive components. Further, a large number of side terminals 11 must be provided, and the insulation between the side terminals 11 is difficult when the side terminals 11 are so dense. PA1 (b) Secondly, an external component 2 is attached on the board through conventional wiring process, and the board 1A or 1B is mounted on a mother board by soldering side terminals 11 to a printed pattern on the mother board. In the structure, the component 2 is supported by the wire 12 of the component 2 itself. However, that structure has the disadvantage that the complicated fine surface pattern 10 on the surface of the board is difficult. PA1 (c) Further, since the structure of a multilayer hybrid circuit is so sophisticated, it is mechanically weak, and is easily damaged. In particular, when a multilayer hybrid circuit is mounted on a conventional printed mother board, a small deformation of a printed mother board would then apply a significant amount of stress to a multilayer hybrid circuit board, and damage the same. PA1 (d) Because of the above disadvantages, the density of electronic components on a laminated hybrid circuit is limited.